The present invention relates to a retention mechanism of a heat sink, and particularly to a retention mechanism for easily securing a heat sink to a central processing unit (CPU) module.
As the operational speed of a CPU increases, a large quantity of heat is produced. The heat may surpass a maximum temperature limit of the CPU and adversely affect normal operation thereof if the heat generated thereof is not effectively dissipated. Therefore, a heat sink is commonly fixed to the CPU for dissipating accumulated heat. Furthermore, a retention mechanism is usually used to firmly secure the heat sink to the CPU for achieving excellent heat dissipation.
A conventional retention mechanism for a heat sink is disclosed in U.S. Pat. No. 5,805,430. A frame in accordance with the conventional retention mechanism is mounted to a support on which a substrate is mounted. The substrate is a printed circuit board, a circuit card, or other similar device. The frame is positioned on the support and comprises a plate above the substrate for supporting a heat sink and several studs surrounding the substrate for securing the frame to the support. The plate defines an aperture through which the heat sink is connected with the substrate. However, the frame is too bulky and occupies too much space on the support. If the support is a mother board, such a retention mechanism can not fulfil practical and economical requirements.
Another kind of the retention mechanism for a heat sink is shown in FIGS. 1 and 2. A CPU module 3 is vertically mounted on a circuit board (not labeled), while a heat sink 2 is also vertically mounted on the circuit board proximate the CPU module 3. A retention mechanism 1 is provided to secure the heat sink 2 to the CPU module 3. The retention mechanism 1 comprises a contracting plate 10 attached to the CPU module 3 and a plurality of mounting legs 60. The mounting legs 60 are pre-fixed to the heat sink 2 and outwardly extend therefrom for extending through corresponding apertures (not shown) defined in the CPU module 3. The contracting plate 10 comprises a handle 11 formed on a bottom edge thereof proximate the circuit board for facilitating manual operation, and a plurality of resilient portions 12 outwardly extending at an incline for resiliently cooperating with the corresponding mounting legs 60. An elongate slot (not shown) is defined in each resilient portion 12 for engaging with the corresponding mounting leg 60. The apertures extends through the contracting plate 10 and communicate with the corresponding elongate slots of the resilient portions 12.
The mounting legs 60 are fixed to the heat sink 2 firstly in assembly. The handle 11 is then upwardly moved to drive the contracting plate 10 upwards thereby permitting the mounting legs 60 to extend through the corresponding apertures and out of the corresponding elongate slots of the contracting plate 10. After the extensions of the mounting legs 60, the handle 11 is released to secure the mounting legs 60 with the contracting plate 10 via the corresponding resilient portions 12.
However, since space on the circuit board is limited, vertical operation of the handle 11 is adversely limited by other electronic elements 5, such as a capacitor. Furthermore, the pre-loaded mounting legs 60 outwardly extend from the heat sink 2 through the CPU module 3 to cooperate with the corresponding resilient portions 12 of the contracting plate 10. Thus, an assembly of the heat sink 2, the CPU module 3 and the retention mechanism 1 is bulky and occupies a large space on the circuit board. Moreover, the assembly is inconvenient for package and transportation. In addition, preloading the mounting legs 60 onto the heat sink 2 is laborious since a convection region 6 of the heat sink 2 has a large quantity of high density heat dissipating plates (not labeled), thereby increasing manufacturing costs.